Smoothing tile boundaries of images encoded and decoded by JPEG 2000

Abstract

An image processing apparatus and method for decompressing compressed image data is described. In one embodiment, the image processing apparatus decompresses compressed image data that is obtained by dividing an original image into blocks and compressing each block. The apparatus may comprise a decompression unit to decompress the compressed image data to provide an image which is a collection of the respective blocks, and a smoothing unit to perform a smoothing operation on the decompressed image to control the smoothing effect applied to the image based on distance from a block boundary and based on an edge amount.

1. An image processing apparatus for generating image data from a code stream coded with the use of wavelet transform, comprising:
 a tag processing unit to interpret tag information added to the code stream and to decompose the code stream into coded streams of respective tiles of respective components; 
 an inverse quantization unit to determine a target bit position to decode in an order based on the tag information and to generate a context from peripheral bits of the target bit; 
 an entropy decoding unit to generate the target bit by decoding with probability estimation with the context and the code stream and to write the target bit in the target bit position; 
 a wavelet inverse transform unit to perform an inverse wavelet transform on the decoded data from the entropy decoding unit and to restore the respective tiles of the respective components of the image data; 
 a color space inverse transform unit to generate the image data with a color space inverse transform from the restored data from the wavelet inverse transform unit; and 
 a tile boundary smoothing unit to perform smoothing processing on a tile boundary of the image data generated by the color space inverse transform unit, wherein: 
 the tile boundary smoothing unit is operable to optimize a range in which a lowpass filter is applied to the image data according to the number of levels of the wavelet transform applied at the time of coding the image data. 
 
     
     
       2. The image processing apparatus as claimed in  claim 1 , wherein:
 the tile boundary smoothing unit applies the lowpass filter to the pixel range of power of 2 of the tile boundary. 
 
     
     
       3. The image processing apparatus as claimed in  claim 1 , wherein:
 the tile boundary smoothing unit applies the lowpass filter having a mask size variable according to the number of levels of the wavelet transform applied at the time of coding of the image data. 
 
     
     
       4. An image processing apparatus for generating image data from a code stream coded with the use of wavelet transform, comprising:
 a tag processing unit to interpret tag information added to the code stream and to decompose the code stream into coded streams of respective tiles of respective components; 
 an inverse quantization unit to determine a target bit position to decode in an order based on the tag information and to generate a context from peripheral bits of the target bit; 
 an entropy decoding unit to generate the target bit by decoding with probability estimation with the context and the code stream and to write the target bit in the target bit position; 
 a wavelet inverse transform unit to perform an inverse wavelet transform on the decoded data from the entropy decoding unit and to restore the respective tiles of the respective components of the image data; 
 a color space inverse transform unit to generate the image data with color space inverse transform from the restored data from the wavelet inverse transform unit; and 
 a tile boundary smoothing unit to perform smoothing processing on a tile boundary part of the image data generated by the color space inverse transform unit, wherein: 
 the tile boundary smoothing unit is operable to optimize a range in which a lowpass filter is applied to the data generated by the wavelet inverse transform unit according to the number of levels of the wavelet transform applied at the time of coding the image data. 
 
     
     
       5. The image processing apparatus as claimed in any one of  claims 1 – 4 , wherein:
 the lowpass filter comprises a lowpass filter vertical to the tile boundary or a cross-shaped lowpass filter. 
 
     
     
       6. An image processing method for generating image data from a code stream coded with the use of wavelet transform, comprising:
 interpreting tag information added to the code stream and decomposing the code stream into coded streams of respective tiles of respective components; 
 determining a target bit position to decode in an order based on the tag information and generating a context from peripheral bits of the target bit; 
 generating the target bit by decoding with probability estimation with the context and the code stream and writing the target bit in the target bit position; 
 performing an inverse wavelet transform on the decoded data and restoring the respective tiles of the respective components of the image data; 
 generating the image data with a color space inverse transform from the restored data; and 
 performing smoothing processing on a tile boundary of the image data generated with the color space inverse transform, including optimizing a range in which a lowpass filter is applied to the image data according to the number of levels of the wavelet transform applied at the time of coding the image data. 
 
     
     
       7. The image processing method as claimed in  claim 6 , wherein performing smoothing processing on a tile boundary of the image data includes applying the lowpass filter to the pixel range of power of 2 of the tile boundary. 
     
     
       8. The image processing apparatus as claimed in  claim 6 , wherein performing smoothing processing on a tile boundary of the image data includes applying the lowpass filter having a mask size variable according to the number of levels of the wavelet transform applied at the time of coding of the image data. 
     
     
       9. An image processing method for generating image data from a code stream coded with the use of wavelet transform, comprising:
 interpreting tag information added to the code stream and decomposing the code stream into coded streams of respective tiles of respective components; 
 determining a target bit position to decode in an order based on the tag information and generating a context from peripheral bits of the target bit; 
 generating the target bit by decoding with probability estimation with the context and the code stream and writing the target bit in the target bit position; 
 performing an inverse wavelet transform on the decoded data and restoring the respective tiles of the respective components of the image data; 
 generating the image data with color space inverse transform from the restored data; and 
 performing smoothing processing on a tile boundary part of the image data generated with the color space inverse transform, including optimizing a range in which a lowpass filter is applied to the data generated by performing the wavelet inverse transform according to the number of levels of the wavelet transform applied at the time of coding the image data. 
 
     
     
       10. The image processing method as claimed in any one of  claims 6 – 9 , wherein:
 the lowpass filter comprises a lowpass filter vertical to the tile boundary or a cross-shaped lowpass filter. 
 
     
     
       11. An article of manufacture having one or more computer readable media storing instructions thereon which, when executed by a system, cause the system to perform an image processing method for generating image data from a code stream coded with the use of wavelet transform, the method comprising:
 interpreting tag information added to the code stream and decomposing the code stream into coded streams of respective tiles of respective components; 
 determining a target bit position to decode in an order based on the tag information and generating a context from peripheral bits of the target bit; 
 generating the target bit by decoding with probability estimation with the context and the code stream and writing the target bit in the target bit position; 
 performing an inverse wavelet transform on the decoded data and restoring the respective tiles of the respective components of the image data; 
 generating the image data with a color space inverse transform from the restored data; and 
 performing smoothing processing on a tile boundary of the image data generated with the color space inverse transform, including optimizing a range in which a lowpass filter is applied to the image data according to the number of levels of the wavelet transform applied at the time of coding the image data.